Study on Tomato Stem Rot Caused by Rhizoctonia Solani and Its Controlling Measures in Zhangye District
|School||Gansu Agricultural University|
|Keywords||tomato stem rot Rhizoctonia solani pathogenicity host resistance controlling effect|
Tomato stem rot,which happened commonly and severely during tomato growth in Zhang Ye district of Gansu province,is an important disease.With the average yield reducing rate of 10%and covering about 5333hm2 each year,the disease yearly caused more than 1.2 thousand yuan loss.So,in this paper,measurements for controlling this disease have been put forward according to the pathogenic biological characteristics and occurring rules,which is important to the sustainable development of local tomato industry.In this paper,the disease have been studied in Zhang Ye district by integrating studies in Lab and field experiments with large area investigation and special site observation.The results are as follow:1.The isolation caused tomato wilt:The Rhizoctonia sp,Fusarium sp,Alternaria sp,Cladosporium sp and a kind of oomycetes that was not identified were obtained from 19 samples with PDA medium and cucumber that was used to entrap the pathogens.Their proportion were 32.0%,45.1%,1.5%,1.2%and 20.2%,respectively.The pathogenicity test results showed that the main pathogens caused tomato wilt were Rhizoctonia sp.,a kind of oomycetes and Fusarium sp.,with incidence rates of 49.5%,53.5%and 13.4%, respectively.2.The identification of Rhizoctonia solani:The pathogens caused tomato stem rot in Zhang Ye district was identified as Rhizoctonia solani Kuhn based on the symptoms, colony shapes with different media,biological characteristics and cell nucleolus stain.The biological tests showed that the mycelium of Rhizoctonia solani could grow from 10℃to 37℃,with the optimum 29℃.And the cell nucleolus stain showed that the cell had 3～8 nucleolus.3.The nutrition utilization ability of Rhizoctonia solan:The mycelium growth was inhibited on medium with D-galactose,lactose,chloralose puriss as C-sources, Whose diameter were smaller than CK after 48 hours by 0.84cm,3.1cm and 3.47cm.There was significant difference between every C-source and CK at p＜0.01.The mycelium grew well on medium with other 8 kinds of C-sources,which showed that the Rhizoctonia solan could utilize more kinds of C-sources.The mycelium grew well on soybean peptone and peptone as N-sources with significant difference between N-sources and CK at p＜0.01. Other 11 kinds of N-source could inhibit the mycelium grow. 4.Host species tests:Pathogenicity tests showed that Rhizoctonia solani from tomato could infect 27 species of grain crops,economical crops,vegetable plant and graze. Helianthus annuus L.,Solanum melongena L.and Medicago sativa L.were the highly sensitive host（the severity was 7 and the incidence rate was higher than 70%）.Citrullus lanatus L.,Luffa cylindrica Roem,Gossypium herbaceum L.,Linum usitatissimum L., Lycopersium esculentum Mill,Vigna sinensis（L.）Savi and so on were sensitive host. Triticum aestivum L.,Zea maydis L.,Fagopyrum esculentum Moeneh.,Helianthus annuus L.Var.,Cucumis sativus L.,Helianthus annuus L.Var.,Cucumis melon L.and Avena fatua L.were middle resistance host（the severity was 3）.Oryzae Sativa L.was high resistance host（the severity was 1 and the incidence rate was 9%）.5.Resistance identification:The resistance of tomato seedling inoculated by Rhizoctonia solani and tomato of variety resistance in fields:In 38 tomato varieties during seedling period,Shiji 1 and Fendu queen were severely sensitive hosts（the severity was 7 and the incidence rate was more 50%）,and Jiafen 15,Shijifenguanwang,Hongbaoshi, Tonghui F1,Xiaguang F1,Hongyangli,American dahongdou 12,Neifan 3,Hongza 2 and Dahong 608 were sensitive hosts.Maofen 802 and Zaofen were middle resistance host and no varieties were immune to Rhizoctonia solani.In the 14 industrial tomato varieties, the incidence rate on Qilianjufen 198,Hongbao 9,Ganhong 2,shifang 15 and Shijixingguang 108 was low but high on Tunhe 8 and Tunhe 46.The results showed that the resistance ability of different varieties to stem rot were different,which could be used to select the resistant varieties in production practice.6.The investigation and measurement of disease happening process and influence factors:Based on the datum obtained from studies in special times and sites, the tomato stem rot firstly happened in the middle of May,the peak emerged during the middle and last ten days of June,and the situation became stabilizing in July.The results of relationship between planting methods and the severity tests showed that direct seeding could resist the pathogeney（the incidence rate was 9.6%）,and that the incidence rate was high（21.3%and 20.5%,respectively）by transplanting method as well as in saline-alkali land.The conventional planting measurement had high incidence rate（as high as 15.6%） and the mound planting measurement had low incidence rate.The plastic film with soil made the incidence rate became low（3.1%）while the plastic film with no soil made he incidence rate became high（10%）.The plastic film with breaking during tomato growth had low incidence rate（1.7%）while the plastic film with no breaking had high incidence rate（4.2%）. 7.Tests of fungicide efficiency:the results showed that the controlling effects were not very good when the fungicide were used before transplanting,while transplanting,or irrigating root at the begin of disease emergence.But controlling effect was well when antagonistic bacteria（the mixture of B1 and B2 with 20×dilution）,3%Xiumiao（with 400×dilution）and Hudi（with 750×dilution）were used,whose controlling effects were 67.8%,55.5%and 59.5%.Furthermore,B1,B2 had obviously promoting growth effects for tomato.8.Integrated management for controlling tomato stem rot:Integrated management for controlling local tomato stem rot including variety selecting and distributing,cultivation management strengthening and fungicides using with reasonable amount and fitting times were also put forward in this paper,which will benefit for the development of tomato industry.